Edymnion,
I have a plug-in now that selects leaky surfaces. When I ran it on the
Tardis model you uploaded it pointed out several leaky edges:
The dome light had a few "extra surfaces." I know Shapeways.com doesn't like those.
The right side vertical panels had a vertex that didn't connect to the horizontal panel.
The handles didn't have surfaces on their rears.
If you'd like a copy of the source code, let me know.
Ron